The present invention relates to an electrically-conductive resin composition and more particularly to an electrically-conductive resin composition superior in mechanical strength and heat resistance.
Heretofore, as methods for producing electrically-conductive resins, there have widely been known (1) a method in which the surface of a thermoplastic resin is subjected to zinc spray, application of an electrically-conductive coating material, or plating, and (2) a method in which an electrically-conductive filler is added to a thermoplastic resin.
However, the above methods (1) and (2) involve the following problems. In the method (1), since reprocessing is performed after molding, a long time and extra equipment are required, which leads to an increased cost. As to durability, extensive use would cause deterioration in adhesion and separation between the resin layer and the electrically-conductive surface layer. In the method (2), such separation problem is not encountered, but it is difficult to incorporate an electrically-conductive filler uniformly into the resin and to obtain uniform moldings.
Thermoplastic resins generally employed for the production of electrically-conductive resins are low and high density polyethylenes, polypropylene, polyvinyl chloride and ethylene-vinyl acetate copolymer. All of these resins, upon incorporation therein of an electrically-conductive resin, are poor in uniform dispersibility and it is very difficult or requires a long time to blend and knead both, thus causing problems, e.g. resin deterioration. Besides, those resins have drawbacks attributable to their intrinsic physical properties. For example, polypropylene is low in impact resistance; polyvinyl chloride is deteriorated in physical properties and heat resistance by migration of plasticizer; and ethylene-vinyl acetate copolymer gives off the small of acetic acid during processing.